Question

Calculate the number of photons emitted in 10 hours by a 60 W sodium lamp (λ of photon = 5893 Å)

Answer 1

Energy emitted by sodium lamp in one sec. = Watt x sec = 60 x 1 J

Energy of photons emitted = hc/λ

= {6.626 x 10³⁴ x 3 x 10⁸}/{5893 x 10^-10} J

= 3.37 x 10^-19 J

No. of Photons emitted per sec. = {60}/{3.37 x 10^-19} = 17.8 x 10¹⁹

∴ Number of photons emitted in 10 hours = 17.8 x 10¹⁹ x 10 x 60 x 60

= 6.41 x 10²⁴